Acharya T, et al. - Researchers assessed long-term outcomes of unrecognized myocardial infarction (UMI) found by cardiac magnetic resonance (CMR) vs clinically recognized myocardial infarction (RMI) and no myocardial infarction (MI). They found that UMI vs no MI carried higher all-cause mortality but was equivalent with RMI within 10 years of baseline evaluation. A higher risk of nonfatal MI and heart failure was observed in relation to UMI.

Methods

• The ICELAND MI cohort study was a population-based study, in which prospectively enrolled participants (aged 67-93 years) were characterized using CMR at baseline (from January 2004-January 2007) and followed up for up to 13.3 years.
• Researchers evaluated the association of UMI at baseline with death and future cardiovascular events by using Kaplan-Meier time-to-event analyses and a Cox regression.
• They mainly assessed all-cause mortality, in addition, a composite of major adverse cardiac events (MACE: death, nonfatal MI, and heart failure) was also evaluated.

Results

• A total of 935 participants including 452 (48.3%) men were included; the mean (SD) age of participants with no MI, UMI, and RMI was 75.6 (5.3) years, 76.8 (5.2) years, and 76.8 (4.7) years, respectively.
• Similar mortality rates (3%) for UMI and no MI were reported at 3 years and these rates were lower than RMI rates (9%).
• Elevated UMI mortality rates (13%) were reported at 5 years, which were higher than no MI rates (8%) but still lower than RMI rates (19%).
• By 10 years, no statistical difference was seen between UMI and RMI mortality rates (49% and 51%, respectively); both were found to be remarkably higher than no MI (30%) (P<.001).
• An increased risk of death (hazard ratio [HR], 1.61; 95% CI, 1.27-2.04), MACE (HR, 1.56; 95% CI, 1.26-1.93), MI (HR, 2.09; 95% CI, 1.45-3.03), and heart failure (HR, 1.52; 95% CI, 1.09-2.14) was reported for UMI by CMR when compared with no MI and statistically nondifferent risk of death (HR, 0.99; 95% CI, 0.71-1.38) and MACE (HR, 1.23; 95% CI, 0.91-1.66) vs RMI, after adjusting for age, sex, and diabetes.